Water
waves are best reflected from hardflat surfacesas
shown in the picture below.

Note that the total length of the line representing the
wave
peak
stays the same where it is being
reflected.
The red part of the incidentwaveplus the blue part of
the reflected
wave
is the same length as the original line.

After reflection a wave
has the samespeed, frequency and wavelength,
it is only the direction of the
wave that has changed.